Cognitive impairments affect up to 36% of the population over age 65 and determine whether an individual may live independently and work competently in older adulthood. After 65, the incidence of dementia increases exponentially. Identifying modifiable contributors to cognitive impairment and inexpensive, safe ways to mitigate cognitive deficits are critical priorities for research and clinical practice. Deficits in cognition are paralleled by changes in sleep in older adulthood. Existing research demonstrates severe consequences of sleep loss on cognition and brain function in young adults. This raises the question of whether sleep deficits common in aging contribute to cognitive deficits prevalent in older adulthood. Cognitive processes that decline with age and depend on the prefrontal cortex (PFC), i.e. executive functions, are most sensitive to individual differences sleep efficiency and sleep depth. Paradoxically, habitual total sleep time is rarely associated with executive function in older adults. In fact, very long total sleep time is commonly associated with poorer cognition and general health. Consequently, sleep restriction does not negatively affect cognition in older adults to the same extent as young adults. This raises the question of whether deeper, more consolidated sleep is better for older adults. There may be a moderate ideal sleep range that optimizes sleep depth to optimize cognition and brain function in older adults. The aim of the proposed study is to behaviorally increase physiological measures of sleep depth (non-REM slow-wave activity) in older adults through time-in-bed restriction, to examine its positive effects on executive function and corresponding functional brain network connectivity. This study's focus is to determine whether effects of sleep depth are greatest for executive functions and corresponding networks. This study will pinpoint systems-level pathways through which sleep promotes cognitive fitness. Broadly, it will contribute to our future development of sleep interventions to improve cognition and our understanding of modifiable health factors that promote cognitive fitness and brain health.